This invention generally relates to screw extruders, and more particularly, to a screw extruder specifically designed to insure a smooth, regular flow of material from a feed hopper and into an extruder barrel.
Typically, a screw extruder comprises an elongated cylinder or barrel, a feed hopper mounted on one end of the barrel, and a rotatable screw axially extending within the barrel. In use, an extrudable material is fed into the hopper, which in turn passes that material into the extruder barrel, and the extruder screw is rotated in the barrel to advance the extrudable material therethrough. The material is then forced from the barrel and, usually, through a nozzle or die that forms the extrudable material into a desired shape.
Near the inlet of the extruder barrel, the rotating extruder screw tends to push the extrudable material toward one side of the barrel. As a result, some extrudable materials, such as some chewing gum compositions, do not always flow smoothly into the extruder barrel from the feed hopper, and instead extrudable material may accumulate on one side of the hopper in the area of the hopper outlet. This interferes with the flow of the extrudable material through the extruder, and in fact might stop that flow. Moreover, the extruder screw may push clogged material upward in the feed hopper, and under certain conditions, material may actually be pushed upwards out of that hopper.